Answer:
Circular tube
Explanation:
Now for better understanding lets take an example
Lets take
Diameter of solid bar= 
cm
Outer diameter of tube =6 cm
Inner diameter of tube=2 cm
So from we can say that both tubes have equal cross sectional area.
We know that buckling load is given as 
If area moment of inertia(I) is high then buckling load will be high.
We know that area moment of inertia(I)
For circular tube 
For circular bar 
Now by putting the values
For circular tube 
For circular bar 
So we can say that for same cross sectional area the area moment of inertia(I) is high for tube as compare to bar.So buckling load will be higher in tube as compare to bar.
Answer:
B- extreme fit, close fit, adjustable fit
Explanation:
A human-fit design typically involves the process of manufacturing or producing products (tools) that are easy to use by the end users. Therefore, human-fit designs mainly deals with creating ideas that makes the use of a particular product comfortable and convenient for the end users.
The design for human-fit strategies include; extreme fit, close fit and adjustable fit.
Hence, when the aforementioned strategies are properly integrated into a design process, it helps to ensure the ease of use of products and guarantees comfort for the end users.
Answer: Solid state welding
Explanation: Solid state welding is the welding procedure which is based on the temperatures and pressure but without any liquid or vapor as aid for welding.This process is carried mainly cohesive forces and considering forces as less important. Brazing,soldering and adhesive is the process in which material are joint which the help of solid welding agent.Thus solid state welding is the correct option.
